As a current mode light-emitting device, an organic light-emitting diode (OLED for short) has been increasingly applied in high-performance organic light-emitting display panels. Referring to FIG. 1, the OLED display panel pixel circuit in the related art includes a driving transistor MD, a transistor M1 functioning as a switch, a capacitor CST and an organic light-emitting device, i.e., 2T1C. The organic light-emitting device includes an organic light-emitting diode DOLED and an inductance capacitor COLED of the organic light-emitting diode DOLED. The transistor M1 is connected to a data signal VDATA and is controlled by a scanning signal VSCAN. The driving transistor MD is connected to a pixel power supply VDD and is also connected to the data signal VDATA via the transistor M1. Two terminals of the capacitor CST are connected respectively to the pixel power supply VDD and a node A between the transistor M1 and the driving transistor MD. The organic light-emitting diode DOLED and the inductance capacitor COLED are connected in parallel between the transistor MD and an external power supply VSS. The voltage of the external power supply VSS is lower than the voltage of the pixel power supply VDD, for example, the voltage of the external power supply VSS can be the ground voltage. When a gate electrode of the transistor M1 responds to scanning signal VSCAN and conducts the transistor ML the capacitor CST is charged based on the data signal VDATA, and then the voltage in the capacitor CST is applied on the gate electrode of the driving transistor MD, thereby conducting the driving transistor MD, so that the organic light-emitting device through which current flows emits light.
The current provided to the organic light-emitting device through the driving transistor MD can be calculated by following formula:IOLED=½*β(VGS−VTH)2  formula 1
IOLED is the current flowing through the organic light-emitting device. VGS is a voltage applied between the gate electrode and the source electrode of the driving transistor MD, and VGS is determined by a voltage across the CST. VTH is a threshold voltage of the driving transistor MD. β is a gain factor of the driving transistor MD, which is determined by a size of the device and a carrier mobility of a semi-conductor. It can be seen from formula, the current flowing through the organic light-emitting device may be affected by the threshold voltage of the driving transistor MD. Since the threshold voltage of each transistor in the organic light-emitting display panel may be different from each other in a production process, as well as an electron mobility of each transistor. On this basis, the current IOLED generated in the circuit is variable even given the same VGS, thereby resulting non-uniformity of brightness.